Funds are requested for purchase of a VG Autospec three-sector double- focusing mass spectrometer equipped with chromatograph and interface, extended mass range, and interchangeable electron-ionization, chemical- ionization, normal and continuous-flow fast-atom bombardment, and field desorption ion sources. The instrument is needed for two purposes. First, it will replace a 10-year old Kratos MS-30 instrument of 20-year old design as one of the only two campus-wide double-focusing mass spectrometers currently providing accurate-mass or fast-atom bombardment (FAB) mass spectra of 3,000 samples per year for OSU researchers. Second apart form its technical performance superiority, the new instrument is vastly simpler to operate and service, and should this significantly improve our mass spectrometry service productivity and reliability. Third, the instrument will provide several important new mass spectrometric capabilities not currently available at Ohio State: continuous-flow FAB, field desorption, and accurate-mass thermospray LC/MS, as well as higher sensitivity (factor of 10 in both EI and FAB), higher mass resolution (60,000 vs.40,000), much higher upper mass limit (4,500 vs. 2,000 u at all full accelerating voltage), and an improved data system compared to our other double-focusing instrument (VG 70-250S). The instrument will be operated an maintained by the permanent staff of the Ohio State University Campus Chemical Instrument Center, which includes three full-time permanent staff mass spectrometrists and an electrical engineer (please see enclosed descriptive brochure), and will be made available campus-wide to all members of the OSU biochemical research community. The NIH-supported "Core Group" of researchers listed below, with a combined annual NIH operating support of more than $2.5 million, currently accounts for more than 80% of the present usage (2,500 samples per year) of our two existing double-focusing instruments .